1. Field of the Invention
The invention relates to a multi-jack detector, and more particularly to a multi-jack detector for detecting states of jacks using a single I/O pin.
2. Description of the Related Art
Along with advances in technologies, a variety of types of jacks, such as Line, Surround, Center, and LFE-Out output jacks are often disposed in a single apparatus. As a result, an electronic device such as an audio card (i.e., a sound card) usually needs a jack detector to detect the state of each jack in order to detect whether external terminals are inserted into the output jacks.
FIG. 1 is a schematic illustration showing the connection between a control unit and multiple phone-jacks. As shown in FIG. 1, the control unit 11 mainly outputs audio signals to each of the phone-jacks PJ1, PJ2 and PJ3, and detects the connection state of each jack. The jack PJ1 outputs main audio signals (Line-out R & L), the jack PJ2 outputs LFE-out audio signals (LFE-out) and the center output audio signals (CEN-out), and the jack PJ3 outputs surround audio signals (Surround-out R & L). Each of the phone-jacks PJ1, PJ2 and PJ3 of the system has at least one switch (e.g., pins 2 and 3 of each jack) to indicate the insertion states of the external terminals. Because in FIG. 1 the system has three phone-jacks PJ1, PJ2 and PJ3, the control unit 11 needs three I/O pins DT1, DT2 and DT3 to receive insertion state signals of the phone-jacks PJ1, PJ2 and PJ3. If the system has five phone-jacks, the control unit 11 needs five I/O pins to receive the insertion state signals of the five jacks. In the integrated circuit (IC) manufacturing processes, the more the number of I/O pins is, the more the manufacturing process costs. Therefore, if the number of I/O pins is reduced, the manufacturing cost of the control unit may be decreased.